1. Field of Invention
The invention relates to a heat dissipating structure, and, in particular, to a fan module and a fan casing.
2. Related Art
As shown in FIG. 1, a conventional fan 1 has an external frame 11 and a fan assembly 12 installed in the external frame 11. In the conventional structure, four screws 13 passing through the external frame 11 are utilized to fasten the fan 1 to a system frame 2. Thus, the fan 1 can be assembled on the system frame 2.
In addition to the screws, an adhesive agent 32 may be applied to a backside of an external frame 31 of a conventional fan 3, as shown in FIG. 2. Thus, the external frame 31 may be assembled on a system frame 2′ by adhering.
However, the method of screwing the external frame to the system frame is laborious and time-consuming. Furthermore, the screws will be loosed after a period of time such that the fan cannot be firmly assembled on the system frame, or even the fan may be damaged due to the loosed screws. In addition, to adhere the external frame to the system frame may consume the cost of the adhesive agent. Besides, if the fan is adhered to the system frame, the fan cannot be easily disassembled from the system frame for replacement, which is very inconvenient.